Gold Coating of Silver Nanoprisms

Core–shell Ag@Au nanoprisms are prepared through a surfactant‐free seed‐mediated approach by taking advantage of the anisotropic structure of silver nanoprisms as seeds. The gold coating on the silver nanoprism surface is achieved by using hydroxylamine as a mild reducing agent, and the final fully gold‐coated prism structures are confirmed by microscopic and spectroscopic characterization. The resulting Ag@Au core–shell structure preserves the optical signatures of nanoprisms and offers versatile functionality and particularly better stability against oxidation than the bare silver nanoprism. The surface plasmon resonances of the core–shell Ag@Au nanoprisms can be tuned throughout the visible and near‐IR range as a function of the Au shell thickness. Such tailorable optical features and surfactant‐free gold shells have great potential applications in biosensing and bioimaging.     

Optical properties of dyes with/without metal nanoparticles doped in a highly ordered nanostructure

Highly ordered nanocomposite arrays of Rh6G-Au-AAO are formed by filling anodized aluminum oxide (AAO) with Rhodamine 6G (Rh6G) and gold nanoparticles. The optical properties of Rh6G-Au-AAO are studied by visible absorptive and fluorescent spectroscopy. Compared with the fluorescence spectra of Rh6G-Au in the solution environment, the fluorescence peak intensities of Rh6G-Au-AAO are significantly enhanced, the maximum enhancement rate is 5.5, and a constant blue shift of ∼12 nm of peak positions is presented. The effects come from the spatial confinement of AAO and the inhibition of the fluorescence quenching effect induced by gold nanoparticles. The results show that the nanocomposite structures of fluorescence molecules-metal nanoparticles-AAO have a considerable potential in engineering molecular assemblies and creating functional materials of superior properties for future nanophotonics.     

High efficiency polymer solar cells with wet deposited plasmonic gold nanodots

We report the enhanced performance of poly(3-hexylthiophene)/[6,6]-phenyl-C₆₁ butyric acid methyl ester (P3HT/PCBM) bulk heterojunction solar cells with wet deposited interfacial gold nanostructures on their indium tin oxide (ITO) surfaces. To produce localized surface plasmons at the ITO surfaces, gold nanostructures were fabricated through the layer-by-layer deposition of gold nanorods onto the ITO substrates and transformed into nanodots through a thermally induced shape transition. The incorporation of plasmonic gold nanodots on the ITO surface was found to result in an increase in the power conversion efficiency from 3.04% to 3.65%, which is due to the presence of the resulting plasmon field.     

Gold Core‐DNA‐Silver Shell Nanoparticles with Intense Plasmonic Chiroptical Activities

The strong plasmonic chiroptical activities of gold core‐DNA‐silver shell nanoparticles (NPs) are reported for the first time, using cytosine‐rich single‐stranded DNA as the template for the guidance of silver shell growth. The anisotropy factor of the optically active NPs at 420 nm reaches 1.93 × 10^?2. Their chiroptical properties are likely induced by the DNA–plasmon interaction and markedly amplified by the strong electromagnetic coupling between the gold core and silver shell.     

Porphyrinic Metal–Organic Frameworks Coated Gold Nanorods as a Versatile Nanoplatform for Combined Photodynamic/Photothermal/Chemotherapy of Tumor

In this paper, a simple, but effective method is reported to construct the core?shell gold nanorod@metal–organic frameworks (AuNR@MOFs) as a multifunctional theranostic platform by using functionalized AuNRs as seed crystal for the growth of porphyrinic MOFs on the surface of AuNR. Such a delicate tunable core?shell composite not only possesses the improved drug loading efficiency, near‐infrared light‐trigger drug release, and fluorescence imaging, but also can produce reactive oxygen species as well as photothermal activity to achieve combined cancer therapy. It is further demonstrated that the camptothecin loaded AuNR@MOFs show distinctively synergistic efficiency for damaging the cancer cell in vitro and inhibiting the tumor growth and metastasis in vivo. The development of this high‐performance incorporated nanostructure will provide more perspectives in the design of versatile nanomaterials for biomedical applications.     

太赫兹表面等离激元及其应用

金属或半导体与介质分界面上的电子与光子互作用形成的光学表面等离激元(SPP)以及人工超构材料或二维原子晶体材料表面上的电子与太赫兹波或微波互作用形成的人工表面等离激元(SSP)是小型化与集成化太赫兹有源/无源器件和太赫兹超分辨率成像的重要物理基础。随着太赫兹科学技术的发展,太赫兹表面等离激元研究在国际上受到很大关注。本文介绍了传统的光学表面等离激元及其发展,详细阐述了太赫兹波段的人工表面等离激元(SSP)和石墨烯表面等离激元(GSP)的基本原理和发展历程,对表面等离激元在太赫兹波段的新型辐射源、无源器件、超分辨率成像及其他领域的应用进行了较为全面的总结和评述,并对该领域未来进一步发展的方向进行了展望。     

Suppression of efficiency roll-off in TADF-OLEDs using Ag-island nanostructures with localized surface plasmon resonance effect

Organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) have emerged as promising alternatives to phosphorescent OLEDs for harvesting both singlet and triplet excitons. However, the development of TADF-OLEDs meets a thorny problem of serious efficiency roll-off at high luminance. Here, we demonstrate an approach to suppress the efficiency roll-off characteristics in TADF-OLEDs by localized surface plasmon resonance (LSPR) effect of easy-fabricated Ag-island nanostructures. Compared with the common TADF-OLEDs at a high current density of 100 mA cm⁻², the efficiency roll-off ratio of the TADF-OLEDs with Ag-island nanostructures decreases from 49.75% to 35.76% significantly, and the maximum current efficiency is increased by 10.5%. The performance enhancement is mainly attributed to the coupling between excitons and localized surface plasmons (LSPs), which could alter the excited state kinetic characteristics of TADF molecules.     

Gold Nanoparticle and Gold Nanorod Embedded PEDOT:PSS Thin Films as Organic Thermoelectric Materials

We report the thermoelectric properties of organic–inorganic hybrid thin films composed of conductive polymer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), and inorganic gold nanomaterials. Two kinds of material with different shapes, namely rod-shaped gold nanorods (AuNRs) and spherical gold nanoparticles (AuNPs), were used in this study. The PEDOT:PSS/AuNR hybrid films showed an enhancement in electrical conductivity (σ ≈ 2000 S cm^?1) and concurrently a decrease in the Seebeck coefficient (S ≈ 12 μV K^?1) with increase in the AuNR concentration. This behavior indicates the presence of the hybrid effect of AuNR on the thermoelectric properties. From scanning electron microscopy (SEM) observation of the highly concentrated PEDOT:PSS/AuNR hybrid films, the formation of a percolated structure of AuNRs was confirmed, which probably contributed to the large enhancement in σ. For the highly concentrated PEDOT:PSS/AuNP films, a dense distribution of AuNPs in the film was also observed, but this did not lead to a major change in the σ value, probably due to the less conductive connections between NPs. This suggests that one-dimensional particles with larger aspect ratio (rods and wires) are favorable nanocomponents for development of highly conductive hybrid materials.     

Plasmon‐Enhanced Fluorescence‐Based Core–Shell Gold Nanorods as a Near‐IR Fluorescent Turn‐On Sensor for the Highly Sensitive Detection of Pyrophosphate in Aqueous Solution

Developing plasmon‐enhanced fluorescence (PEF) technology for identifying important biological molecules has a profound impact on biosensing and bioimaging. However, exploration of PEF for biological application is still at a very early stage. Herein, novel PEF‐based core–shell nanostructures as a near‐infrared fluorescent turn‐on sensor for highly sensitive and selective detection of pyrophosphate (PPi) in aqueous solution are proposed. This nanostructure gold nanorod (AuNR)@SiO₂@meso‐tetra(4‐carboxyphenyl) porphyrin (TCPP) contains a gold nanorod core with an aspect ratio of 2.3, a silica shell, and TCPP molecules covalently immobilized onto the shell surface. The silica shell is employed a rigid spacer for precisely tuning the distance between AuNR and TCPP and an optimum fluorescence enhancement is obtained. Due to the quenching effect of Cu²⁺, the copper porphyrin (TCPP‐Cu²⁺) results in a weak fluorescence. In the presence of PPi, the strong affinity between Cu²⁺ and PPi can promote the disassembly of the turn‐off state of TCPP‐Cu²⁺ complexes, and therefore the fluorescence can be readily restored. By virtue of the amplified fluorescence signal imparted by PEF, this nanosensor obtains a detection limit of 820 × 10^?9m of PPi with a good selectivity over several anions, including phosphate. Additionally, the potential applicability of this sensor in cell imaging is successfully demonstrated.     

Coupled surface plasmon resonance on bimetallic films covered by sub-micrometer polymer gratings

Angular interrogation investigation of the rotated grating-coupled surface plasmon resonance was performed, via exciting plasmons on special sensing layers by a frequency doubled continuous Nd:Yag laser beam in Kretschmann arrangement. NBK7 glass substrates were evaporated by silver and gold layers having appropriate thicknesses to ensure a narrow plasmon resonance peak. Thin poly-carbonate films spin-coated onto the bimetallic layers were patterned by the fourth harmonic of a pulsed mode Nd:Yag laser applying a master grating-based interference method. The pulsed force mode atomic force microscopic investigation has shown the existence of a surface relief grating and a coexistent adhesion modulation having a period of 416 nm. The conditions of the grating-coupling effect were determined for shallow sub-micrometer polymer gratings, and secondary minima were detected on the resonance curves measured in presence of polymer patterns, according to the calculations. The indispensability of a minimal modulation amplitude and the existence of an optimal rotation angle of the grating grooves with respect to the plasmon propagation direction were experimentally proven. The position of the emerged secondary resonance minimum indicated that the average film thickness was decreased caused by material removal during the structure formation. It was shown by tapping-mode AFM that the sub-micrometer adhesion modulation resulted in periodic adherence of streptavidin in the structure’s valleys. The attachment of a small amount of protein was detected based on the shift of the secondary resonance peak. The capability of the polymer grating for sensitivity enhancement was demonstrated, proving that the secondary peak shift is highly sensitive to the protein concentration. The application of the polymer grating covered bimetallic films as transducing layers in novel bio-sensorization method based on rotated grating coupling is proposed.     

具有分形结构Ag纳米衬底的荧光增强效应

利用电化学沉积方法,制备出具有分形结构的Ag纳米荧光增强衬底。实验中,采用532nm连续光激发居于Ag纳米结构衬底表面附近的罗丹明6G(Rh6G)荧光分子,结果表明,具有分形结构的Ag纳米金属衬底对沉积在其表面的Rh6G分子表现出明显的荧光增强效应。根据局域场增强理论对所得实验结果进行分析,经过电化学方法制备出的分形Ag纳米结构,在外电磁场激发下能够形成较强的局域电磁场分布,从而有效地激发Rh6G荧光分子,增强其荧光辐射强度。     

Spectral encoding on Gold Nanorods Doped in a Silica Sol–Gel Matrix and Its Application to High‐Density Optical Data Storage

Metallic nanorods exhibit fascinating optical properties due to surface plasmons—collective oscillation of the electron cloud within a particle. They exhibit two principle absorption bands that correspond to surface plasmon resonance (SPR) along the longitudinal and transverse directions of the nanorod. Most importantly, the longitudinal band can be tuned with the aspect ratio of the rod, making it a spectrally tuneable optical material, which can be applied to a variety of devices from bioimaging to high‐density optical storage. Here, spectral encoding for high‐density optical storage applications is demonstrated on two sizes of gold nanorods (aspect ratios of three and five) doped in a silica sol–gel matrix by femtosecond pulsed laser irradiation. It is widely known that high‐power pulsed laser irradiation causes metal nanorods to undergo shape transformations via the process of melting or fragmentation. The process is enhanced if the laser wavelength is tuned at the longitudinal surface plasmon resonance peak of the nanorods, which results in a significant reduction or shift in the surface plasmon resonance peak. As such a shape change occurs only on the subpopulation of rods that have a longitudinal plasmon band matching the laser wavelength, a size‐ or spectrum‐selective shape transition is possible in a rod mixture with varying aspect ratios. The current spectral encoding technology can be incorporated into existing optical disc technology, such as three‐dimensional bit‐by‐bit and holographic, and can increase the capacity limit by utilizing the spectral domain.     

Monodisperse Polymer Capsules: Tailoring Size,Shell Thickness,and Hydrophobic Cargo Loading via Emulsion Templating

The preparation of monodisperse polymer (polydopamine, PDA) capsules by a one‐step interfacial polymerization of dopamine onto dimethyldiethoxysilane (DMDES) emulsion droplets and removal of the DMDES templates with ethanol is reported. The diameters of the PDA capsules can be tailored from 400 nm to 2.4 µm by varying either the DMDES emulsion condensation time or the emulsion concentration used for templating. Further, capsules with defined nanometer‐scale shell thicknesses (ranging from ～10 to 30 nm) can be prepared by adjusting the emulsion concentration. This shell thickness can be increased by repeated interfacial polymerization of dopamine, with three cycles yielding capsules with a shell thickness of up to 140 nm (for a 0.6% v/v suspension). Functional substances, such as organically stabilized magnetic (Fe₃O₄) nanoparticles, quantum dots (CdSe/CdS), and hydrophobic drugs (thiocoraline), can be preloaded in the emulsion droplets, and following PDA coating and DMDES removal, these materials remain encapsulated in the polymer capsules. All of the unloaded and loaded PDA capsules are monodisperse and do not aggregate. This work provides new avenues for the preparation of polymer capsules with defined size and shell thickness and for the encapsulation of a range of hydrophobic substances.     

Inhibition of Cancer Cell Migration by Gold Nanorods: Molecular Mechanisms and Implications for Cancer Therapy

Gold nanorods have received much attention because of their distinct physicochemical properties and promising applications in bioimaging, biosensing, drug delivery, photothermal therapy, and optoelectronic devices. However, little is known regarding their effect on tumor metastasis. In the present investigation, serum protein‐coated gold nanorods (AuNRs) at low concentrations is shown to exhibit no apparent effects on the viability and proliferation of three different metastatic cancer cell lines, that is, MDA‐MB‐231 human breast cancer cells, PC3 human prostate cancer cells, and B16F10 mouse melanoma cells, but effectively inhibit their migration and invasion in vitro. Quantitative proteomics and real‐time PCR array analyses indicate that exposure of cells to AuNRs can down‐regulate the expression of diverse energy generation‐related genes, which accounts for their inhibition of mitochondrial oxidative phosphorylation (OXPHOS) and glycolysis. The impairment of OXPHOS and glycolysis results in a distinctive reduction of ATP production and subsequent inhibition of F‐actin cytoskeletal assembly, which is crucial for the migration and invasion of cancer cells. The inhibitory effect of AuNRs on cancer cell migration is also confirmed in vivo. Taken together, the unique mechanism in inhibiting cancer cell migration by AuNRs might provide a new approach to specific cancer therapeutic treatment.     

Plasmon–Exciton Interactions: Spontaneous Emission and Strong Coupling

The extraordinary optical properties of surface plasmons in metal nanostructures provide the possibilities to enhance and accelerate the spontaneous emission, and manipulate the decay and emission processes of quantum emitters. The extremely small mode volume of plasmonic nanocavities also benefits the realization of plasmon–exciton strong coupling. Here, the progress on the study of plasmon modified spontaneous emission and plasmon–exciton strong coupling are reviewed. The fundamentals of surface plasmons and quantum emitters, and the methods for assembling coupling systems of plasmonic nanostructures and quantum emitters are first introduced. Then the major aspects of plasmon modified spontaneous emission, including emission intensity, lifetime, spectral profile, direction, polarization, and energy transfer are reviewed. The coupling of quantum emitters and plasmonic waveguides is then discussed. Next, the developments of strong coupling between plasmonic structures and various quantum emitters are reviewed. Finally a few applications are highlighted followed by conclusions and outlook.     

Constructing Superhydrophobicity by Self-Assembly of SiO2@Polydopamine Core-Shell Nanospheres with Robust Oil-Water Separation Efficiency and Anti-Corrosion Performance

Vulnerable robustness of superhydrophobic materials have mightily hindered their practical applications. Herein, a controllable and effective strategy is demonstrated for constructing robust superhydrophobicity with aqueous hydrophobic interaction driving self-assembly (HIDS), using polydopamine (PDA) as the binder and SiO₂ particles as the nano-sized structures to enable low-adhesive property. The proposed strategy realizes the rapid interfacial assembly of PDA by manipulating the wetting properties of SiO₂@PDA core-shell particles with hydrophobic modifier. The polyurethane (PU) sponges are facilely rendered superhydrophobic with remarkable robustness, stemming from the excellent adherence of HIDS enhanced covalent interaction between PDA and PU. Coated sponge possesses ultralong-term stability during the oil-water separation, the separation efficiency can be maintained at 98.8% even after 1000 cycle separations and strikingly, superhydrophobicity is still retained after 100 cycle abrasion with ultrahigh loading pressure of 49 kPa. Versatilely, the coatings can be assembled on various substrates through scalable dip coating for attaining superhydrophobicity, regardless of size, roughness, chemistry, and rigidity. The complete water-repellent coatings on permanent magnet of Nd-Fe-B hold excellent anti-corrosion properties without deteriorating the magnetic properties, exhibiting a low corrosion current density of 2.03 × 10⁻⁸ A cm⁻², which is three orders of magnitude lower than that of 1.30 × 10⁻⁵ A cm⁻² for bare Nd-Fe-B magnet.     

Atomic-Precision Tailoring of Au–Ag Core–Shell Composite Nanoparticles for Direct Electrochemical-Plasmonic Hydrogen Evolution in Water Splitting

Traditionally, bandgap materials are a prerequisite to photocatalysis since they can harness a reasonable range of the solar spectrum. However, the high impedance across the bandgap and the low concentration of intrinsic charge carriers have limited their energy conversion. By contrast, metallic nanoparticles possess a sea of free electrons that can effectively promote the transition to the excited state for reactions. Here, an atomic layer of a bimetallic concoction of silver–gold shells is precisely fabricated onto an Au core via a sonochemical dispersion approach to form a core–shell of Au–Ag that exploits the wide availability of excited states of Ag while maintaining an efficient localized surface plasmon resonance (LSPR) of Au. Catalytic results demonstrate that this mix of Ag and Au can convert solar energy to hydrogen at high efficiency with an increase of 112.5% at an optimized potential of −0.5 V when compared to light-off conditions under the electrochemical LSPR. This outperforms the commercial Pt catalysts by 62.1% with a hydrogen production rate of 1870 µmol g⁻¹ h⁻¹ at room temperature. This study opens a new route for tuning the range of light capture of hydrogen evolution reaction catalysts using fabricated core–shell material through the combination of LSPR with electrochemical means.     

3D Visible-Light-Driven Plasmonic Oxide Frameworks Deviated from Liquid Metal Nanodroplets

Eutectic gallium-indium (EGaIn) liquid metal droplets have been considered as a suitable platform for producing customized 3D composites with functional nanomaterials owing to their soft and highly reductive surface. Herein, the synthesis of a 3D plasmonic oxide framework (POF) is reported by incorporating the ultra-thin angstrom-scale-porous hexagonal molybdenum oxide (h-MoO₃) onto the spherical EGaIn nanodroplets through ultrasonication. Simultaneously, a large number of oxygen vacancies form in h-MoO₃, boosting its free charge carrier concentration and therefore generating a broad surface plasmon resonance across the whole visible light spectrum. The plasmonic chemical sensing properties of the POF is investigated by the surface-enhanced Raman scattering detection of rhodamine 6G (R6G) at 532 nm, in which the minimum detectable concentration is 10⁻⁸ m and the enhancement factor reached up to 6.14 × 10⁶. The extended optical absorption of the POF also allowed the efficient degradation of the R6G dye under the excitation of ultraviolet-filtered simulated solar light. Furthermore, the POF exhibits remarkable photocurrent responses towards the entire visible light region with the maximum response of ≈ 1588 A W⁻¹ at 455 nm. This work demonstrates the great potential of the liquid metal-based POFs for high-performance sensing, catalytic, and optoelectronic devices.     

Large‐Area Fabrication of Periodic Arrays of Nanoholes in Metal Films and Their Application in Biosensing and Plasmonic‐Enhanced Photovoltaics

Plasmonics is a fast developing research area with a great potential for practical applications. However, the implementation of plasmonic devices requires low cost methodologies for the fabrication of organized metallic nanostructures that covers a relative large area (～1 cm²). Here the patterning of periodic arrays of nanoholes (PANHs) in gold films by using a combination of interference lithography, metal deposition, and lift off is reported. The setup allows the fabrication of periodic nanostructures with hole diameters ranging from 110 to 1000 nm, for 450 and 1800 nm of periodicity, respectively. The large areas plasmonic substrates consist of 2 cm × 2 cm gold films homogeneously covered by nanoholes and gold films patterned with a regular microarray of 200 μm diameter circular patches of PANHs. The microarray format is used for surface plasmon resonance (SPR) imaging and its potential for applications in multiplex biosensing is demonstrated. The gold films homogeneously covered by nanoholes are useful as electrodes in a thin layer organic photovoltaic. This is first example of a large area plasmonic solar cell with organized nanostructures. The fabrication approach reported here is a good candidate for the industrial‐scale production of metallic substrates for plasmonic applications in photovoltaics and biosensing.     

Ultrathin Polydopamine Films with Phospholipid Nanodiscs Containing a Glycophorin A Domain

Cellular membranes have long served as an inspiration for nanomaterial research. The preparation of ultrathin polydopamine (PDA) films with integrated protein pores containing phospholipids and an embedded domain of a membrane protein glycophorin A as simplified cell membrane mimics is reported. Large area, ultrathin PDA films are obtained by electropolymerization on gold surfaces with 10–18 nm thickness and dimensions of up to 2.5 cm². The films are transferred from gold to various other substrates such as nylon mesh, silicon, or substrates containing holes in the micrometer range, and they remain intact even after transfer. The novel transfer technique gives access to freestanding PDA films that remain stable even at the air interfaces with elastic moduli of ≈6–12 GPa, which are higher than any other PDA films reported before. As the PDA film thickness is within the range of cellular membranes, monodisperse protein nanopores, so‐called “nanodiscs,” are integrated as functional entities. These nanodisc‐containing PDA films can serve as semi‐permeable films, in which the embedded pores control material transport. In the future, these simplified cell membrane mimics may offer structural investigations of the embedded membrane proteins to receive an improved understanding of protein‐mediated transport processes in cellular membranes.